1. Field of the Invention
The present invention relates to an attitude control device for controlling the attitude or direction of a member to be driven such as a rotational shaft, a probe or the like. More specifically, the present invention pertains to an attitude control device having a plurality of harmonic drive mechanisms of the hollow type. The present invention also relates to a drilling-direction control device for a drilling system for oil wells or the like, wherein a plurality of harmonic drive mechanisms of the hollow type are utilized to orient a rotational drill shaft to a desired direction, to thereby control the drilling direction of a drill bit mounted on the end of the rotational drill shaft.
2. Related Art Statement
In various technical fields, attitude or direction control of, for example, a rotational shaft or the like is regarded a highly important technique for enabling a desired motion or operation of a member to be driven. For example, in the machine tool field, the cutting bit or the workpiece have to be precisely brought to a desired position for accurate machining.
On the other hand, in oil well drilling, a controller is provided for varying the drilling direction of a drill bit so as to avoid rock beds. The drilling-direction controller serves also to adjust the drilling direction of the drill bit so that it is precisely oriented in the target direction. Examples of drilling-direction controllers are disclosed, for example, in U.S. patent application Ser. No. 6/158948 filed on Jun. 12, 1980, U.S. Pat. No. 4,303,135 issued to Lloyd F. Benoit on Dec. 1, 1981, and Japanese Patent Public-Disclosure Nos. SHO 57-100290 disclosed on Jun. 22, 1982 and SHO 58-210300 disclosed on Dec. 7, 1983.